Classic Celluloid Picks - One of the first polymers ever created, cellulose nitrate is made by reacting cotton fibres with nitric acid. Used for more than a century as the base for movie and 35mm film, celluloid was substituted for natural tortoise shell picks in the early 1900s. Still one of the most popular pick materials available today, they are available in a variety of thicknesses, shapes and colours, and provide a natural feel and a warm, fat tone.